The present invention relates to methods and apparatus used to control the pressure around and above a substrate. More particularly, the present invention relates to improved wafer area pressure control rings.
In the fabrication of semiconductor-based devices (e.g., integrated circuits) layers of material may alternately be deposited onto and etched from a substrate (e.g., the semiconductor wafer). As is well known in the art, the etching of the deposited layers may be accomplished by a variety of techniques, including plasma enhanced etching. In plasma-enhanced etching, the actual etching of the substrate takes place inside a plasma processing chamber. During etching, a plasma is formed from a suitable etchant source gas to etch areas of the substrate that are unprotected by the mask, leaving behind the desired pattern.
Among different types of plasma etching systems, those utilizing confinement rings have proven to be highly suitable for efficient production and/or for forming the ever shrinking features on the substrate. An example of such a system may be found in the commonly assigned U.S. Pat. No. 5,534,751, which is incorporated by reference herein. Although the use of confinement rings results in a significant improvement in the performance of plasma processing systems, current implementations can be improved. In particular, it is realized that improvements can be made in the way in which confinement rings are maintenanced and replaced. More particularly, significant improvements can be made in the way in which these rings are attached within the chamber.
To facilitate discussion, FIG. 1 depicts a current wafer area pressure (WAP) ring hanger assembly. The prior art design as shown by FIG. 1, required a technician to the hold the WAP ring assembly 100 in place, while another technician fastened screw 105 and clamp 130 to suspend the ring from the plunger shaft 115 of the upper chamber assembly. Although not shown in FIG. 1, but known to those of ordinary skill in the art, typically the pressure ring assembly 100 is attached at three points, each spaced 120 degrees from one another, further complicating assembly.
The ring assembly 100 is typically a composite of 4 rings which (the top ring, ring no. 4, 125 being the thickest) according to desired pressure requirements can be raised or lowered with the aid of the stepped hanger 110. The operation of removing and reinstalling the WAP ring assembly has been identified as an ergonomic safety issue. Additionally, the use of tools and fasteners in conjunction with the installation and removal of the WAP rings increases the opportunity for ring damage, dropping of parts (e.g., screws and washers) into the pump, as well as an increased time component for replacement. It should be noted that the stepped hanger 110 is one continuous piece, i.e., the stepped portion is attached directly to the plunger shaft 115.
The combined hanger/stepped hanger design of the prior art is also unwieldy because while the technician is attaching the hanger to the plunger shaft, the quartz rings are loosely floating and must be securely held while the technician secures the screw 105 to the plunger shaft 115. Accordingly, it is desirable to simplify the removal and installation of these rings.